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Visual Awareness  9

                    Perhaps John fails to eat because his hands are temporarily paralyzed,
                    because he has been influenced by a hypnotic suggestion, or whatever.
                    This problem undercuts the claim that behavioral analyses of mental
                    states are elegant and insightful, suggesting instead that they are fatally
                    flawed or at least on the wrong track.
                    2. Inability to eliminate mental entities. The other problem is that the con-
                    ditionals that must be enumerated frequently make reference to just the
                    sorts of mental events that are supposed to be avoided. For example,
                    whether John sees the food or not, whether he intends to fast, and what he
                    believes about its being poisoned are all mentalistic concepts that have now
                    been introduced into the supposedly behavioral definition. The amended
                    version is therefore unacceptable to a strict theoretical behaviorist.
                 For such reasons, theoretical behaviorism ultimately failed. The problem, in a
               nutshell, was that behaviorists mistookthe epistemic status of mental states
               (how we come to know about mental states in other people) for the ontological
               status of mental states (what their inherent nature is) (Searle, 1992). That is, we
               surely come to know about other people’s mental states through their behavior,
               but this does not mean that the nature of these mental states is inherently
               behavioral.
               Functionalism  Functionalism was a movement in the philosophy of mind that
               began in the 1960s in close association with the earliest stirrings of cognitive
               science (e.g., Putnam, 1960). Its main idea is that a given mental state can be
               defined in terms of the causal relations that exist among that mental state,
               environmental conditions (inputs), organismic behaviors (outputs), and other
               mental states. Note that this is very much like behaviorism, but with the im-
               portant addition of allowing other mental states into the picture. This addition
               enables a functionalist definition of hunger, for example, to refer to a variety
               of other mental states, such as perceptions, intentions, and beliefs, as sug-
               gested above. Functionalists are not trying to explain away mental phenomena
               as actually being propensities to behave in certain ways, as behaviorists did.
               Rather, they are trying to define mental states in terms of their relations to
               other mental states as well as to input stimuli and output behaviors. The picture
               that emerges is very much like information processing analyses. This is not
               surprising because functionalism is the philosophical foundation of modern
               computational theories of mind.
                 Functionalists aspired to more than just the overthrow of theoretical behav-
               iorism, however. They also attempted to blockreductive materialism by sug-
               gesting new criticisms of mind-brain identity theory. The basis of this criticism
               lies in the notion of multiple realizability: the fact that many different physical
               devices can serve the same function, provided they causally connect inputs and
               outputs in the same way via internal states (Putnam, 1967). For example, there
               are many different ways of building a thermostat. They all have the same
               function—to control the temperature in the thermostat’s environment—but
               they realize it through very different physical implementations.
                 Multiple realizability poses the following challenge to identity theory. Sup-
               pose there were creatures from some other galaxy whose biology was based
               on silicon molecules rather than on carbon molecules, as ours is. Let us also
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